1. Field of the Invention
This invention relates to a method, a portable data carrier, a release apparatus and a system for releasing a transaction using acceleration sensors.
2. Related Art
According to this application an acceleration sensor will be understood to be a sensor that ascertains the acceleration of a body, for example by determining the inertial force acting on a test mass. There are known according to the prior art semiconductor-based acceleration sensors and rotation sensors. Such an acceleration sensor measures linear self-motions and accelerations and subsequently, on the basis of the measurement result, triggers switching operations in dependence on the self-motion in space. A rotation sensor ascertains the rotational self-motion around an axis. Merely by way of example, the single-axis rotation sensor LY530AL and the three-axis rotation sensor LIS344ALH from the company ST Microelectronics are stated as electronic components here.
The possibility of integrating a motion sensor into a portable data carrier, in particular in the form of a chip card, is known from the laid-open application DE 102 48 389. The motion sensor is used here exclusively for capturing lettering.
A problem of portable data carriers consists in the fact that they can be read out via a contactless interface from a distance, for example through a pocket, unnoticed by the owner. Especially critical in this connection is the possibility of a relay attack, because here a connection is set up via a radio link to an “authentic” reading device. Such an attack is described for example in Chapter 8 of the book “Handbuch für Chipkarten” by Rankl, Effing or in Chapter 8 of the book “RFID-Handbuch” by Finkenzeller. The relay attack is also referred to in the literature as a ghost-and-leech attack.
According to the prior art it is proposed to avoid this problem by for example equipping portable data carriers with a push-button. The installation of a push-button in a chip card or security token is very elaborate, however, and causes high production costs. Being a mechanical component, a push-button is furthermore always subject to wear and can also cause difficulties due to contact problems.
From the publication “RFIDs and Secret Handshakes: Defending Against Ghost-and-Leech Attacks and Unauthorized Reads with Context-Aware Communications”, published at the 15th ACM Conference of Computer and Communications Security 2008, pages 479 to 490, there is known the possibility of capturing characteristic gestures using an acceleration sensor in order to release the access to a data carrier.
This use of gestures seems impracticable from today's point of view. With passive portable data carriers which are equipped without a battery, the range for making gestures is of a similar size to the range in which communication can be effected at all between the portable data carrier and an end device, in particular a reading device, because power is available to the data carrier for performing its measurements and calculations only in this range. Upon the use of reading devices according to ISO/IEC 14443 with a typical range of for example 10 cm, the latitude for motion for making a gesture within the reading range of a card is thus greatly limited. In addition, there is a possible psychological barrier to making complex gestures with the portable data carrier on an end device, for example a POS terminal or a transport ticket machine in public.
From the patent print EP 1 745 420 B1 it is known, on the other hand, to design the card body of a chip card with an inhomogeneous material. The characteristic self-oscillations arising from the material of the card upon excitation of the chip card are evaluated and the chip card thereby identified. This method appears very cost-intensive, because each card body must be individual.
The object of the present invention is therefore to show a method, a system, a portable data carrier and a release apparatus with which the release of a transaction between a portable data carrier and an end device is effected more cost-efficiently, more securely more easily.
A transaction will be understood according to this application to be a logical sequence of operations. A transaction is for example a payment operation between a portable data carrier and an end device via a contactless interface. A transaction is alternatively also the readout of security-critical information, for example PIN numbers, personal data or general secrets, such as TAN numbers, passwords and so forth.